Israel continued its assault on Palestinian towns throughout the West Bank Friday even as U.S. peace envoy Anthony Zinni met with Palestinian leader Yasser Arafat, who has been trapped in his office here for a full week.

The mastermind of the Passover Massacre suicide bombing that killed 26 people last week was reported killed when the Israelis entered Tubas, a town of 20,000. It was Israel's first foray into the town.

Attack helicopters battled hundreds of gunmen in Nablus and nearby refugee camps. Smoke from burning cars and shops rose from downtown Nablus and frightened residents huddled in the innermost rooms of their apartments.

Two Palestinian militia leaders were killed, including alleged bombing mastermind Qeis Odwan, who headed Izzedine al Qassam, the military wing of the Islamic militant group Hamas, Hamas sources and Israel TV said.

Odwan and five other members were killed when their hide-out in Tubas was shelled, sources and TV said. The army had no comment.

Izzedine al Qassam has carried out a series of suicide bombings in Israel, including the Passover attack on March 27 and a bombing in the northern port city of Haifa on March 31, in which 15 people were killed.

In Nablus, Nasser Awais, leader of the Al Aqsa Martyrs' Brigade, was killed when explosives strapped to his body went off prematurely, said a militia spokesman, Abu Mujahed. The Al Aqsa militia is linked to Arafat's Fatah movement.

More than 40 Palestinians, including several gunmen and a 14-year-old girl, were killed Friday and early Saturday. The Israeli military also retrieved the bodies of five men in Bethlehem, apparently killed by fellow Palestinians as suspected informers for Israel. At least one Israeli soldier was also killed.

Israel's offensive continued despite a tough speech by President Bush on Thursday in which he demanded that Israel halt its incursions and announced he would send Secretary of State Colin Powell to the region next week. Bush also accused Arafat of not confronting terrorists, and said his difficult situation was largely of his own making.

Zinni met for 90 minutes Friday with Arafat, becoming the first senior official in eight days to meet with the Palestinian leader, who has been confined by Israel to a few rooms in his West Bank headquarters since last week.

Arafat adviser Nabil Abu Rdeneh said there would be more meetings between Palestinian and U.S. officials later in the day. Palestinian negotiator Saeb Erekat later said that Israel was preventing the follow-up talks, a claim Israel denied.

Arafat's deputy, Mahmoud Abbas, said Arafat told Zinni that the Palestinians support a cease-fire deal negotiated last year by CIA chief George Tenet.

Also Friday, an Israeli helicopter fired missiles on a car in Hebron driven by Ziyad Shuweiki of the Islamic Jihad militant group, but he escaped, witnesses said. They said five bystanders, including an 8-year-old boy, were injured. The Israeli military had no immediate comment.

Despite Bush's demand that Israel halt its week-old offensive, Israeli Defense Minister Binyamin Ben-Eliezer said Friday that "we are continuing the operation we started."

Israel has occupied six main Palestinian towns and several smaller ones, and hundreds of Palestinians have been arrested.

In Bethlehem, a standoff between Israeli forces and about 240 gunmen holed up in the Church of the Nativity, built over the site where tradition says Jesus was born, entered a fourth day. Four of about 60 priests trapped in the church came out Friday and left Bethlehem under Israeli escort, the military said.

Giacomo Bini, a senior Roman Catholic official in Rome, said both Israel and the Palestinian gunmen have caused damage the shrine, one of Christianity's holiest. Witnesses have said gunmen shot open a door when they forced their way into the church Tuesday, and the Palestinians have said Israeli forces blew open a door leading into the church courtyard Thursday.

In the Gaza Strip, some 10,000 supporters of Hamas rallied in the Jebaliya refugee camp. Sheik Ahmed Yassin, the Hamas founder, said the group would not stop attacks on Israelis, and he accused the United States of trying to weaken the Palestinians' resolve by renewing truce efforts.

Also Friday, Israeli soldiers fired tear gas and stun grenades at journalists trying to cover the Zinni-Arafat meeting, and tanks pointed barrels at the group.

Israel had initially turned down Zinni's request to see Arafat, but relented after Bush's speech Thursday. Powell called Arafat early Friday, Abu Rdeneh said.

In Friday's fighting, Israeli tanks rolled into Tubas, the first Israeli incursion since Bush demanded a halt to such raids. A 14-year-old Palestinian girl was killed by Israeli tank fire as she watched the scene from her balcony, Palestinian witnesses said.

The heaviest fighting was reported in the old city of the West Bank town of Nablus, the adjacent refugee camp of Balata and the refugee camp of Jenin to the north — three strongholds of Palestinian gunmen.

Israeli helicopters and tanks fired shells and machine guns at the gunmen, who fired from behind barricades, witnesses said. Two people were killed in Jenin and nine in Nablus and Balata, witnesses and doctors said.

In Nablus, doctors opened a makeshift hospital in a mosque because ambulances could not enter, they said.

On Thursday, four Israeli soldiers were killed, including three in intense fighting at the Jenin camp.

In a statement Friday, the Israeli military said it is holding 900 Palestinian prisoners and has confiscated 50 anti-tank grenades and two launchers, 26 machine guns, nine bombs, four belts for suicide bombers, dozens of boxes of ammunition, scores of kilograms of explosives, more than 1,300 rifles and more than 670 pistols.

The Associated Press contributed to this report.